How to add custom fields to capture more about your subscribers

Every subscriber is more than an email address. Where they signed up, which plan they're eyeing, their birthday, their company size — that's the data that lets you send "here's the Growth plan you looked at" instead of "Dear customer." Custom fields are how you capture it. A custom field adds a column to your list, gives you a merge tag to drop that value into any email, and becomes something you can filter on when you build a segment.

This guide adds a custom field from scratch, end to end, so by the finish you can collect a new piece of data, personalize with it, and target by it.

Who this is for: anyone managing a mailing list who wants to collect more than name and email. You'll work on the customer side, inside one of your lists — no admin access needed.

Before you start#

• A list to add the field to — custom fields belong to a single list. Go to Audience → Lists and open the one you want to extend.
• Know what you're collecting — a piece of data with a clear use: "plan interest" to tailor offers, "signup source" to see what's working, "birthday" to send a date-triggered email. If you can't name how you'll use it, don't collect it.

Step 1 — Open Manage list fields#

Open your list, then click the Manage list fields tab. This screen lists every field on the list — the built-in ones (Email, First Name, Company, Date of Birth…) plus any custom fields you add. Each row shows the field's name, its type, and — the important part — its merge tag, like {{ SUBSCRIBER_FIRST_NAME }}. That tag is how you reference the value later.

One rule to know up front: the Email field is required and can't be removed. Everything else is yours to add, reorder, hide, or delete.

The Manage list fields tab lists every field with its type and its merge tag ({{ SUBSCRIBER_… }}). Email is required and can't be removed; everything else is yours to manage.

Step 2 — Add and configure a field#

Scroll to the Add field row at the bottom and click the type that fits your data. Grouped by what they do:

• Text — a short free-text answer (job title, city).
• Number — a numeric value you can compare (team size, order count).
• Dropdown / Radio — one choice from a fixed list you define.
• Multi-select / Checkbox — one or more choices from a fixed list.
• Date / Date & time — a calendar value (birthday, renewal date).
• Text area — a longer free-text answer.
• Phone — a phone number.

A new field row appears, expanded, ready to configure:

• Label — what you (and your signup form) call the field, e.g. Plan interest.
• Tag — the merge tag's name. It's auto-prefixed SUBSCRIBER_, so typing PLAN_INTEREST gives you {{ SUBSCRIBER_PLAN_INTEREST }}. This is the token you'll use in emails and segments.
• Default value — an optional value used when a subscriber leaves it blank.
• Required — force a value at signup.
• Visible — show the field on your signup forms (turn it off for data you set yourself, like a score or tag).
• Options — for a Dropdown, Multi-select, Checkbox, or Radio, add each choice as a label — value pair (e.g. Starter — starter). Click Add option for more.

Fill it in, then click Save fields at the bottom.

A Dropdown field being configured: a Label, its auto-generated merge tag, and the choices as label — value pairs. Number, Date, Text and the rest share the same Label / Tag / Required / Visible controls.

Tip: Keep tags short and stable. The merge tag is baked into every email and segment that uses the field, so renaming it later means updating those references. Pick PLAN_INTEREST once and leave it.

Step 3 — Use your new field#

A custom field earns its keep in two places, both powered by that merge tag:

• Personalize emails. Drop {{ SUBSCRIBER_PLAN_INTEREST }} into a subject line or body and each recipient sees their own value — "Ready to move up to Growth?" See advanced merge tags for fallbacks and formatting.
• Target with segments. The moment you save the field, it shows up as a condition when you build a segment — so you can send only to Plan interest equals growth. That's the payoff below.

Right after saving, "Plan interest" is selectable as a segment condition — filter your list by the data you just started collecting. See the full segment walkthrough for how to stack conditions.

And when you import contacts from a CSV, your new field appears in the field-mapping step, so you can map a spreadsheet column straight into it.

Field types — which to pick#

• Filtering or math later (counts, sizes) → Number.
• A fixed set of answers you'll segment on → Dropdown (one) or Multi-select (several) — cleaner than free text, which is easy to mistype.
• A date you'll trigger emails from → Date.
• Anything freeform → Text (short) or Text area (long).

Choosing a structured type (Dropdown/Date/Number) over plain Text pays off at segment time — you filter on clean values instead of guessing at typos.

Troubleshooting#

• The field doesn't show on my signup form → turn on Visible for it. Fields with Visible off exist on the list but aren't shown to subscribers (useful for internal values you set yourself).
• The merge tag prints literally in an email → check the tag spelling matches exactly (case included). {{ SUBSCRIBER_PLAN_INTEREST }} only resolves if that's the field's real tag; a typo renders as plain text.
• I can't find the field as a segment condition → save the field first (Save fields), then reopen the segment builder — conditions read the list's saved fields.
• I need to remove a field → use Delete field on its row. Note this drops that column's data for every subscriber, so export first if you might want it back. The Email field has no delete — it's required.

Recap#

You've added a custom field: opened Manage list fields, picked a type, named it and its merge tag, set its options and visibility, and saved. Now you can collect that data, personalize emails with {{ SUBSCRIBER_… }}, and target it in a segment.

Next, turn that field into an audience in Build a subscriber segment, and put the merge tag to work in Personalization beyond first name.